Impact properties of carbon fiber reinforced linear and short-chain branched polyethylenes

Summary An investigation of the influence of short-chain branched length on impact behavior of linear high density polyethylene (HDPE), short-chain branched polyethylenes (SBPEs) and their fiber reinforced samples is reported. The result shows that the total impact energies (E_t) increased with increasing branch length at any given temperature used in this study. Similar trend was found for their fiber reinforced samples. For a given polyethylene resin, E_t increased with fiber content up to 5%, and then decreased consistently with further increase of fiber content. The amount of E_t improved due to the presence of 5% carbon fibers increased significantly with the branch length at temperatures higher than 25°C. In addition, the fracture surface morphology indicated that the adhesion between carbon fibers and PE resins increased with the branch length. However, the adhesion and the amount of E_t improved due to the presence of 5% carbon fibers reduced significantly with decreasing temperature. Finally, it was found that E_t decreased slightly with rising temperature until the temperature reached around 40°C, and then increased sharply with increasing temperature. It is suggested that this transition behavior is related to the molecular motion accounting for the transition of PE resins.